AU2013211449A1 - A fluid actuator with internal safety locking mechanism - Google Patents

Abstract

A fluid actuator having an internal safety locking mechanism including inter alia cooperative 5 locking means between the actuator's piston rod and the actuator's cylinder adapted to lock and unlock the piston in an extended and retracted position. - 6- T7,I '-I

Description

A FLUID ACTUATOR WITH INTERNAL SAFETY LOCKING MECHANISM FIELD OF THE INVENTION: 5 This invention relates to pneumatic and hydraulic actuators or rams. In particular but not exclusively it relates to a hydraulic actuator having an internal safety locking mechanism. The invention without limiting its scope concerns prevention of the operational, accidental or inadvertent failure of hydraulic rams when extended under pressure. 10 BACKGROUND ART: The use of hydraulic (and pneumatic) actuators in heavy machinery and especially the earth moving industry is known prior art. This generally involves the use of implement engaging fluid activated couplers which are attached to the articulated operating arms of earth moving equipment such as back hoes, diggers, bulldozers and the like. In most all cases it involves the 15 use of couplers with quick release latch assemblies adapted to engage universal standardised implement mount fittings. The implements or tools themselves are of significant mass and weight. Due to the rugged operational conditions and heavy wear and tear on equipment, accidental detachment of the implements can occur often with disastrous consequences. As the implements are generally of a great mass and weight there is a significant safety issue on 20 construction sites. To alleviate the possibility of fatal accidents, various safety devices on prior art couplers have been developed. Among such safety devices are included manually inserted stop pins or locking bolts which rely on human effort and diligence for their successful implementation and operation. Furthermore, as these devices are often one off workshop innovations and are often improvised to solve a particular problem, knowledge of their 25 utilisation and implementation is often not relayed to successive operators. There is therefore a great need for inbuilt and/or automatically deployable safety mechanisms associated with equipment. Ideally, such a device or apparatus would be automatically deployed when an actuator is extended or deployed and deactivated when the actuator is to be retracted without the requirement of human intervention. 30 In addition as actuators are used in many different applications and industries, failure due to loss of hydraulic fluid pressure can have dire consequences. There is a general need to be able to deploy safety mechanisms without significant modification or intervention. Any effort in - 1 having to manually adjust or apply safety mechanisms which requires an operator to manually operate the equipment, will no doubt have a high probability of non compliance and/or failure. 5 OBJECT OF THE INVENTION: It is an object of the invention to provide a novel and inventive solution to the limitations and disadvantages of the prior art. Specifically in a preferred embodiment, the invention relates to a hydraulic actuator having an internal safety locking mechanism. Other aims and advantages of the invention may become apparent from the following description. 10 STATEMENT OF THE INVENTION In one aspect, the invention resides in a fluid actuator having an internal safety locking mechanism including in combination: an actuator piston extendible and retractable from an actuator cylinder; 15 the actuator piston in sealing connection with an internal wall of the actuator cylinder; cooperative locking means between the piston and the cylinder adapted to lock and unlock the piston in an extended and a retracted position ; the cooperative locking means comprising one or more circumferential raised projections on the surface of the piston rod forming a backstop or a ratchet, respectively; 20 a gland to seal the piston rod with the cylinder; the gland including one or more spring biased spools or pins adapted to engage the backstop or ratchet to lock the piston in an extended position; fluid pressure in a first circuit to extend the piston wherein the spools or pins are overridden by the backstop or a ratchet until they engage a projection at the end of the piston's extension, and 25 fluid pressure in a second circuit to overcome the spring bias of and withdraw the spools or pins and to retract the piston. Preferably, the one or more circumferential raised projections have a barbed shape or configuration which overrides and pushes back the spools or pins as the piston is extended 30 which then spring up behind the projection to lock the position of the extended piston. Preferably, the spools or pins are biased to engage the backstop or ratchet by compression springs. -2- Actuator piston 2 is extendible and retractable from actuator cylinder 3 and is in sealing connection with the internal wall of actuator cylinder 3a. Actuator piston rod 2a has one or more circumferential raised projections 4, 5 on its surface 5 comprising a ratchet. Actuator cylinder has a gland 6 with one or more spring biased spools or pins 7, 8 adapted to engage ratchet to lock the piston in an extended position. Hydraulic pressure in a first circuit 9a extends piston wherein the ratchet overrides the spring biased spools or pins. Hydraulic pressure in a second circuit 9b retracts piston on first withdrawing the spools or pins from the ratchet. 10 Figure 2 shows a perspective view of an actuator piston assembly 2 with circumferential raised projections 4, 5 on its surface which comprise the ratchet. It will of course be realised that while the foregoing has been given by way of illustrative 15 example of this invention, all such and other modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of this invention as is herein set forth. In addition, throughout the specification the terms "comprising" and "containing" shall be 20 understood to have a broad meaning similar to the term "including" and will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. This definition also applies to variations on the terms "comprising" and "containing" such as "comprise", "comprises", "contain" and "contains". 25 -4-

Claims (5)

1. A fluid actuator having an internal safety locking mechanism including in combination: 5 an actuator piston extendible and retractable from an actuator cylinder; the actuator piston in sealing connection with an internal wall of the actuator cylinder; cooperative locking means between the piston and the cylinder adapted to lock and unlock the piston in an extended and a retracted position ; the cooperative locking means comprising one or more circumferential raised projections on the surface of the piston rod forming a 10 backstop or a ratchet, respectively; a gland to seal the piston rod with the cylinder; the gland including one or more spring biased spools or pins adapted to engage the backstop or ratchet to lock the piston in an extended position; fluid pressure in a first circuit to extend the piston wherein the spools or pins are overridden by 15 the backstop or a ratchet until they engage a projection at the end of the piston's extension, and fluid pressure in a second circuit to overcome the spring bias of and withdraw the spools or pins and to retract the piston.

2. The actuator of Claim 1 wherein the one or more circumferential raised projections have a 20 barbed shape or configuration which overrides and pushes back the spools or pins as the piston is extended which then spring up behind the projection to lock the position of the extended piston.

3. The actuator of Claim 1 wherein the spools or pins are biased to engage the backstop or 25 ratchet by compression springs.

4. The actuator of Claim 1 wherein the fluid pressure in the second circuit against the spring bias causes withdrawal of the spools or pins from the backstop or ratchet before retracting the piston. 30

5. The actuator of Claim 1 wherein the actuator can be disassembled into its component parts for repair and/or maintenance purposes. -5-